1. Technical Field
The present invention relates to a pivot bearing for a swing arm for swingably supporting a magnetic head in a hard disk drive device.
2. Description of the Prior Art
A hard disk drive device of a larger capacity is required, so that the density of the tracks on the magnetic disk, i.e. the storage medium, is increased accordingly. On the other hand, however, there is strong demand for reduction of the cost of manufacturing the same.
It is, therefore, necessary to reduce the cost for manufacturing, to enhance the accuracy of rotation of the magnetic disk, to control precisely the position of the magnetic head for writing data onto the magnetic disk and/or reading therefrom. In this connection, a swing arm for supporting the magnetic head must have a structure which can be pivoted with high precision, in order to displace the magnetic head accurately.
In other words, a pivot bearing of high precision in its rotation must be used for rotatable support of the swing arm. Further, it is necessary to facilitate the operation for mounting the swing arm to the pivot bearing and the operation for mounting the pivot bearing to the hard disk drive device to reduce the number of operations required therefor and to reduce the cost of manufacturing the same.
One of the swing arm supporting structures of the prior art is illustrated in FIG. 6. In FIG. 6, reference numeral 31 is given to a base of the hard disk drive device, reference numeral 32 is given to a shaft extending vertically from the base. The structure further includes a pair of upper and lower ball bearings 33 and 34, the inner rings of which are mounted around the outer periphery of the shaft 32, and a cylindrical bearing holder 35 mounted around the outer rings of the ball bearings. A swing arm 36 is adapted to be fit around the outer periphery of the bearing holder 35 by fitting a vertical through hole 37a extending through a cylindrical fitting portion 37 formed on the base of the arm. The swing arm 36 is secured to the bearing holder 35 by any means such as an adhesion.
In the swing arm assembly of the prior art as described above, the precision required in processing and assembling the bearing holder 35 to be interposed between the ball bearings 33, 34 and the fitting cylinder 37 of the swing arm is substantially the same level as that required for processing and assembling the upper and lower ball bearings.
Thus the number of parts of the swing arm assembly of the prior art is relatively large. Control of the precision of these parts is difficult. These are the difficulties encountered in reducing the cost for manufacturing the hard disk drive device.